Coating Boxes

The usual form for iodine and bromine boxes is see, at figs. 14 and 15. They are far superior to those in use with the English operators. Each consists of a wooden box (a,) having firmly embeded within it a stout glass jar (c), the edges of which are ground. Over this is placed the sliding cover b, double the length of the box, one half occupied by a piece of ground glass (e), tightly pressed upon the glass pot by a spring (i) beneath the cross bar g, and fits the pot so accurately that it effectually prevents the escape of the vapor of the iodine, bromine or other accelerating liquid contained therein. The other half of the lid is cut through, shoulders being left at the four angles for the different sizes of frames, designed to recieve the plate while undergoing the coating process. When the plate is put into the frame, the cover b is shoved under the second lid h and when coated to the proper degree, it resumes its former position and the plate is placed in the holder of the camera box. To test the tightness of the box, light a piece of paper, put it into the pot and cover it with the sliding lid. The burning paper expels the air from the pot, and if it be perfectly tight you may raise the whole box by the lid.